Heretofore, there has been known as a numerically controlled chamfering apparatus for a glass plate of this kind a chamfering apparatus disclosed in Japanese Unexamined Patent Publication 37040/1984. The numerically controlled chamfering apparatus for a glass plate comprises a fitting holder for setting a glass plate having a desired shape horizontally and a chamfering wheel provided at the upper side of the fitting holder so as to be movable to a desired position by two driving systems having an X axis and a Y axis intersecting the X axis perpendicularly, wherein the chamfering wheel comprises a Z axis system which horizontally turns an arm supporting the chamfering wheel by a servo motor, and the arm has the same center axis as that for turning horizontally in the horizontally turning mechanism, the arm having a degree of freedom around the central axis as a supporting point. As the arm has such degree of freedom, problems of an error in shape of a glass plate, an error in position of the glass plate and so on can be eliminated.
In the numerically controlled chamfering apparatus for a glass plate disclosed in Japanese Unexamined Patent Publication No. 37040/1984, however, there were problems that because a point for driving by the X and Y driving systems did not coincide with a point for grinding the glass plate, (1) it was unavoidable that a speed of grinding at a corner portion greatly decreased in comparison with that at a linear portion, and (2) a centrifugal force was produced at a swing arm and a wheel spindle at the corner portion, however, there was no back-up system. As a result, it was difficult to uniformly chamfer the peripheral edge of a glass plate.
Further, since the shape of glass plates to be supplied are slightly different from each other. The diameter of the chamfering wheel becomes small due to wearing. In a case of the replacement of a chamfering wheel, the function of grinding of a fresh chamfering wheel is different from that of the chamfering wheel which has been replaced. In such cases, the conventional numerically controlled chamfering apparatus for a glass plate could not cope enough with a change of the function of grinding of the chamfering wheel or another change, and there were a disadvantage that a quantity of chamfering varies for products.